I just spent three hours trying to update the firmware on my Dell dock from a Linux environment. Solution: quietly weep, revert to Windows (for a few minutes to run the .exe from Windows boot disk).
Before anyone starts trying to troubleshoot it, yes, I tried all the things in fwupdmgr. Even went so far as to install snap because Dell’s Linux tool required it, and that failed as well.
There’s FreeDos too, you just throw the exe on there and boot to it and run the exe via the dos prompt. I know Linux should let you too.